This invention relates generally to inflatable restraint systems and, more particularly, to an apparatus and method for inflating an inflatable device such as an inflatable vehicle occupant restraint airbag cushion, such as used in such systems.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an "airbag," that is inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins being inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as "inflator."
Many types of inflator devices have been disclosed in the art for inflating an inflatable restraint systems airbag cushion. Prior art inflator devices include compressed stored gas inflators, pyrotechnic inflators and hybrid inflators. Unfortunately, each of these types of inflator devices has been subject to certain disadvantages such as greater than desired weight and space requirements, production of undesired or non-preferred combustion products in greater than desired amounts, and production or emission of gases at a greater than desired temperature, for example.
In view of these and other related or similar problems and shortcomings of prior inflator devices, a new type an inflator, called a "fluid fueled inflator," has been developed. Such inflators are the subject of commonly assigned Smith et al., U.S. Pat. No. 5,470,104, issued Nov. 28, 1995; Rink, U.S. Pat. No. 5,494,312, issued Feb. 27, 1996; and Rink et al., U.S. Pat. No. 5,531,473, issued Jul. 2, 1996, the disclosures of which are fully incorporated herein by reference.
Such an inflator device utilizes a fuel material in the form of a fluid, e.g., in the form of a gas, liquid, finely divided solid, or one or more combinations thereof, in the formation of an inflation gas for an airbag. In one such inflator device, the fluid fuel material is burned to produce gas which contacts a quantity of stored pressurized gas to produce inflation gas for use in inflating a respective inflatable device.
The proper storage of a fuel material together with a corresponding oxidant can be difficult, especially over prolonged period of times such as may be associated with inflatable restraint systems in automotive vehicles, which systems require a responsive lifetime which extends for a period of years. Also, while the separate storage of the fuel and oxidant can alleviate or reduce some such storage concerns, the complexity of the design and manufacture of an inflator providing such separate storage of fuel and oxidant can be more complicated and costly than desired.
While the above-identified fluid fueled inflators avoid or minimize at least some of the above-identified shortcomings of prior inflator devices, there remains a need for an inflator device which satisfies one or more of the following objectives: increased simplicity of design and construction; avoids or minimizes the risks or problems associated with the storing, handling and dispensing of various and selected gas generant materials; and permits even further reductions in assembly weight.
The above-identified related prior application, now patent Rink, U.S. Pat. No. 5,669,629, issued Sep. 23, 1997, discloses and claims airbag inflation gas generation via a decomposing material and specifically discloses acetylene (C.sub.2 H.sub.2) as one decomposable material useable therein.
In the past, acetylene has been used as a fuel material in various industrial applications including, for example, welding and metal cutting. Advantageous thermodynamic and physical properties of acetylene, such as a relatively high calorific content (1307 kJ/mol) and flame temperature (3300.degree. C. in oxygen), make acetylene particularly well suited for such applications. At relatively low pressures (e.g., at pressures as low as about 25 psi), however, acetylene is generally unstable, thus generally rendering the use of acetylene more difficult and typically necessitating the taking of special precautions relative to the handling and use thereof. For example, pure acetylene stored at pressures above about 25 psi is susceptible to reaction, even in the absence of an oxidant. As a result, acetylene is commonly stored absorbed in acetone which, in turn, is held in cylinders filled with a porous filler material.
Thus, an airbag inflator device and method for inflating an inflatable device which at least either simplifies or facilitates the use therein of one or more fuel materials, such as acetylene, such as by avoiding or minimizing the risks normally associated with the storage or handling of the fuel material, have been desired and are sought.